Through their brilliant presentation of a wealth of scientific evidence--from anthropological and behavioral to climatological and genetic--the authors go far to demolish the ""multi-regional hypothesis,"" the belief that human races arose almost two million years ago and evolved separately from one another. Instead, contend Stringer (director of the Human Origins Group at the Natural History Museum, London) and McKie (science editor of the Observer), present-day humans emerged from Africa approximately 100,000 years ago and swiftly colonized the rest of the world, displacing all other hominid species in the process. The authors also argue convincingly that their version of human evolution trivializes a search for differences among the races. While there are superficial variations in appearance, the astounding genetic similarity of humans is the real story: ""We have extenuated the minute differences between ourselves, sometimes with grievous results,"" they write. Amid the spate of books in recent years that have discussed various aspects of human evolution, this intellectually potent yet eminently accessible volume, previously published to acclaim in Britain, stands tall. It provides broad insight into a complex field, and fulfills the authors' aim of wanting ""to help us understand what it means to be human."" Rights (except first serial and electronic): Brockman Inc. (July)